In this study bone regeneration between porous beta-tricalcium phosphate (Conduit TCP) and biphasic calcium phosphate ceramic (Biosel), with a hydroxyapatite/beta-TCP ratio of 75/25, was compared. The ceramic particles were implanted in sheep trabecular bone for 3, 12, and 26 weeks. Histomorphometrical analysis revealed that Conduit degraded significantly during time and only 36% of the material was left at 26 weeks implantation time. Biosel, in contrast, remained nearly intact. The degradation of Conduit was due to dissolution as well as cell-mediated. Biosel showed a high cellular intervention, although this material did not degrade. Both materials were osteoconductive. The amount of newly formed bone appeared greater in the Conduit group after 26 weeks (46% +/- 8% as compared to 37% +/- 8% for Biosel), but this difference was not significant. Bone distribution over the defect was homogeneous in Conduit, whereas Biosel showed significantly more bone in the periphery of the defect after 26 weeks in comparison to the center. In conclusion, both ceramics are biocompatible and osteoconductive. Degradation showed a difference in amount and in cellular events, with more degraded Conduit TCP with less cellular intervention as compared to Biosel.